Automatic tank filling installations used in refineries normally comprise a frame overhanging a track along which tanks move one after another. A duct, which is generally telescopic, is mounted on the frame and can be vertically moved along its axis to enable it to be inserted into a filling orifice in a tank in position below the frame. Since it is not easy to position the tank accurately under the installation, the filling duct is often mounted on a slide which is movable on the frame in the longitudinal direction of the track, so that the duct can be aligned with the orifice.
This longitudinal positioning facility may be insufficient, because the orifice may not be exactly along the tank axis because, after a while, the orifice may become offset, for example, due to improper mounting on the frame, or sagging of the suspension.
To obviate this disadvantage, the tanks are monitored and those which are out of line beyond a certain limit are removed for repairs. Of course, this operation is expensive and it is desirable to increase the out-of-line tolerance threshold so that the tanks can be used longer before repairs.
To accommodate the lack of alignment of the orifices, it has already been proposed to mount the slide bearing the duct so that it can move not only longitudinally but also transversely, so that the duct can be brought exactly above the center of the orifice.
Usually, however, it is found that the displacement of the tank results in an inclination of the tank and therefore of the axis of the orifice. For this reason it may be insufficient to move the duct transversely to bring it above the orifice, because, with the axis of the orifice inclined to the vertical, the horizontal section of the orifice is reduced in the transverse direction, particularly since the tank inlet defining the orifice has a lateral wall which has an appreciable height. Consequently, unless there is a considerable clearance between the duct and the lateral walls of the orifice, the duct will not be able to penetrate into the orifice even after being moved transversely into alignment therewith. Consequently a further reduction has to be made in the permitted lack of alignment of the orifice. For tanks on railway tracks, if the duct has to be lowered into the tank orifice to find out whether it can penetrate into it, and it is then found that the duct will not penetrate into the orifice, the truck will then have to be detached and removed from the train, which of course is very laborious and wastes considerable time.